1,537 research outputs found
On the void explanation of the Cold Spot
The integrated Sachs-Wolfe (ISW) contribution induced on the cosmic microwave
background by the presence of a supervoid as the one detected by Szapudi et al.
(2015) is reviewed in this letter in order to check whether it could explain
the Cold Spot (CS) anomaly. Two different models, previously used for the same
purpose, are considered to describe the matter density profile of the void: a
top hat function and a compensated profile produced by a Gaussian potential.
The analysis shows that, even enabling ellipticity changes or different values
for the dark-energy equation of state parameter , the ISW contribution
due to the presence of the void does not reproduce the properties of the CS.
Finally, the probability of alignment between the void and the CS is also
questioned as an argument in favor of a physical connection between these two
phenomena
Exploring two-spin internal linear combinations for the recovery of the CMB polarization
We present a methodology to recover cosmic microwave background (CMB)
polarization in which the quantity is linearly combined at
different frequencies using complex coefficients. This is the most general
linear combination of the and Stokes parameters which preserves the
physical coherence of the residual contribution on the CMB estimation. The
approach is applied to the internal linear combination (ILC) and the internal
template fitting (ITF) methodologies. The variance of of the resulting map
is minimized to compute the coefficients of the linear combination. One of the
key aspects of this procedure is that it serves to account for a global
frequency-dependent shift of the polarization phase. Although in the standard
case, in which no global E-B transference depending on frequency is expected in
the foreground components, minimizing is
similar to minimizing and separately (as previous methodologies proceed), multiplying
and by different coefficients induces arbitrary changes in the
polarization angle and it does not preserve the coherence between the spinorial
components. The approach is tested on simulations, obtaining a similar residual
level with respect to the one obtained with other implementations of the ILC,
and perceiving the polarization rotation of a toy model with the frequency
dependence of the Faraday rotation.Comment: 14 pages, 8 figures, 2 tables. Accepted for publication in MNRA
Searching for a dipole modulation in the large-scale structure of the Universe
Several statistical anomalies in the CMB temperature anisotropies seem to
defy the assumption of a homogeneous and isotropic universe. In particular, a
dipole modulation has been detected both in WMAP and Planck data. We adapt the
methodology proposed by Eriksen et al. (2007) on CMB data to galaxy surveys,
tracing the large-scale structure. We analyse the NRAO VLA Sky Survey (NVSS)
data at a resolution of ~2 degrees for three different flux thresholds: 2.5,
5.0 and 10.0 mJy respectively. No evidence of a dipole modulation is found.
This result suggests that the origin of the dipole asymmetry found in the CMB
cannot be assigned to secondary anisotropies produced at redshifts around z =
1. However, it could still have been generated at redshifts higher or lower,
such as the integrated Sachs-Wolfe effect produced by the local structures.
Other all-sky surveys, like the infrared WISE catalogue, could help to explore
with a high sensitivity a redshift interval closer than the one probed with
NVSS.Comment: 6 pages, 2 figures. Some minor changes have been done from the
original manuscript. This paper is accepted by MNRA
Radial derivatives as a test of pre-Big-Bang events on the Planck data
Although the search for azimutal patterns in cosmological surveys is useful
to characterise some effects depending exclusively on an angular distance
within the standard model, they are considered as a key distinguishing feature
of some exotic scenarios, such as bubble collisions or conformal cyclic
cosmology (CCC). In particular, the CCC is a non-stardard framework which
predicts circular patterns on the CMB intensity fluctuations. Motivated by some
previous works which explore the presence of radial gradients, we apply a
methodology based on the radial derivatives to the latest release of
\textit{Planck} data. The new approach allows exhaustive studies to be
performed at all sky directions at a HEALPix resolution of . Specifically, two different analyses are performed focusing on weight
functions in both small (up to a -degree radius) and large scales. We
present a comparison between our results and those shown by An et al. (2017),
and An et al. (2018). In addition, a possible polarization counterpart of these
circular patterns is also analysed for the most promising case. Taking into
account the limitations to characterize the significance of the results,
including the possibility of suffering a look-elsewhere effect, no strong
evidence of the kind of circular patterns expected from CCC is found in the
\textit{Planck} data for either the small or the large scales.Comment: 8 figures, 4 table
Manejo de cuencas en Argentina : conceptos, diagnóstico y aspectos institucionales
Fil: Vich, Alberto I. J.Fil: Cobos, Daniel R..Fil: Lenzano, Luis E.
M2LADS: A System for Generating MultiModal Learning Analytics Dashboards
In this article, we present a Web-based System called M2LADS, which supports the integration and visualization of multimodal data recorded in learning sessions in a MOOC in the form of Web-based Dashboards. Based on the edBB platform, the multimodal data gathered contains biometric and behavioral signals including electroencephalogram data to measure learners' cognitive attention, heart rate for affective measures, visual attention from the video recordings. Additionally, learners' static background data and their learning performance measures are tracked using LOGCE and MOOC tracking logs respectively, and both are included in the Web-based System. M2LADS provides opportunities to capture learners' holistic experience during their interactions with the MOOC, which can in turn be used to improve their learning outcomes through feedback visualizations and interventions, as well as to enhance learning analytics models and improve the open content of the MOOC
Bases para un racional manejo de los recursos naturales en ecosistemas desértico : inventario de los cuerpos de hielo en la cuenca del río Malargüe, provincia de Mendoza
Fil: Cobos, Daniel R.
- …